With the increasing down-scaling of integrated circuits (IC) and increasingly demanding requirements to the speed of ICs, transistors need to have higher drive currents with increasingly smaller dimensions. Fin field-effect transistors (FinFET) were thus developed. In a typical finFET, a vertical fin structure is formed over a substrate. This vertical fin structure is used to form source/drain regions in the lateral direction and a channel region in the fin. A gate is formed over the channel region of the fin in the vertical direction forming a finFET. Subsequently, an inter-layer dielectric (ILD) and a plurality of interconnect layers may be formed over the finFET.
Low-power and high-speed circuits are desired in current electronic applications such as smart phones, PDAs, notebooks, and so on. Compared to traditional substrate/fin materials (e.g., silicon), other semiconductor materials (e.g., germanium, silicon germanium, or other group III/group IV/group V elements) has higher mobility and lower effective mass, which benefits the drive current of Field-Effect-Transistors (FETs). Therefore, these other semiconductor materials are promising materials for the next-generation of FETs.